1. Field of the Invention
The present invention relates to an apparatus for measuring the relative distance of a moving body with respect to a mark or the position of the moving member so as to guide the traveling of the moving body along a predetermined traveling path on the basis of the measured results.
2. Description of the Related Art
Conventionally, as a method of guiding the traveling of a moving body along a predetermined traveling path, a guiding method which is generally called a dead-reckoning is known. In this method, the position and traveling direction of the moving body are estimatively calculated on the basis of outputs of a direction detector and a travel length detector, and the steering of the moving body is controlled so as to cause the moving body to pass a predetermined passing point taught in advance on the basis of the estimatively calculated results.
The drawback of this method is that a cumulative error corresponding to a traveled distance occurs in the estimatively calculated result, and a calculation error occurs in the calculation of numerical values, thereby making it impossible for the moving body to pass a predetermined passing point accurately. This is attributable to the fact that in a case where, for instance, an angular velocity sensor is used as the aforementioned direction detector, a cumulative error or a drift error occurs in a detected value when the angular velocity is integrated, or a detection error due to irregularities of a road surface, skidding and the like of wheels occurs in the detected value of the travel length detector.
Accordingly, it has been the general practice to dispose marks at intervals along a predetermined traveling path, and to intermittently correct the estimated position and the estimated traveling direction by recognizing the marks, and various applications for patent have been filed.
As a technique of this type, as disclosed in Japanese Patent Unexamined Publication No. 217787/1986, a method is known in which light-reflecting mirrors are installed at intervals on both sides of a predetermined traveling path, light projecting/receiving devices are provided for projecting light beams from a side of a moving body toward the light-reflecting mirrors and for receiving the light reflected from the light-reflecting mirrors, and the position and traveling direction of the moving body are corrected and calculated on the basis of outputs of the light received by the light projecting/receiving devices, the positions of installation of the light-reflecting mirrors, and so on.
With the conventional techniques, however, it is necessary to provide the moving body with three or more sets of light projecting/receiving devices, and two or more light-reflecting mirrors are required for one correction. When a multiplicity of optical systems are thus provided, the reliability of the apparatus inevitably declines. Accordingly, development of an apparatus capable of effecting correction by using a smaller number of optical systems is desired.
In addition, with regard to the position and traveling direction of the moving body, the positions of installation of the light projecting/receiving devices, the directions of the light projected, the positions of installation of the light-reflecting mirrors, and the like are calculated as known values. Accordingly, in the event that accurate values are not obtained due to the inaccurate survey of the positions of installation of the light-reflecting mirrors or the presence of installation errors at the time of installation, the correction accuracy of the calculated position and traveling direction of the moving body becomes deteriorated. Thus, it is desired to develop an apparatus which is capable of accurately correcting the position and traveling direction of the moving body even when there are errors in the positions of installation of the light projecting/receiving devices and in the directions of the light projected. In addition, since much labor is required in the surveying of the positions of installation of the light-reflecting mirrors, it is desired to alleviate such labor.
As a predetermined traveling path along which a moving body travels, there is a closed loop-type traveling path, and there are cases where the moving body travels along the closed-loop traveling path many times. Here, when the moving body is made to travel along this closed-loop traveling path on the basis of consecutive information on the position and the direction, unless the information on the position and direction of the moving body at a starting point is accurate, the position and direction of the moving body at the same starting point when the moving body has made one circuit deviate substantially from a position and a direction that are desired. Accordingly, it is necessary to cause the moving body to travel accurately by imparting accurate information on the position and direction at the starting point each time the moving body makes one circuit.
In addition, with the light-beam projecting/receiving devices, in a case where the power of the light beam projected is large, there is a problem in safety. At the same time, light reflected from a light-reflecting object other than the light-reflecting mirrors installed is received, so that there is a problem in reliability. If the power of the light beam is conversely made small, it becomes impossible to obtain reflected light at the reflecting mirrors from which the light beam is to be reflected, which presents a problem in reliability. Accordingly, a light beam of a predetermined power is projected, However, in this case as well, portions of the surface of the reflecting mirror may have stains which prevent the reflection. When the light beam is applied to this stained portion, or when the moving body moves irregularly due to rolling, bounding or the like and the light beam is not applied to the reflecting mirror, the reception of the reflected light becomes impossible, thereby presenting a problem in reliability. In addition, the problem of receiving the light reflected from a light-reflecting object other than the relevant reflecting mirror still remains unresolved.
In addition, in a case where the traveling of the moving body is guided along a predetermined traveling path on the basis of the result of measurement of the relative distance of the moving body with respect to a mark, even when the moving body is traveling along a straight line or making a turn in an orbiting manner, it always becomes necessary to determine the relative distance with a high degree of accuracy.